How to add captcha to User Submission Posts plugin

I think this is a duplicate post:

https://wordpress.org/support/topic/how-to-add-captcha-to-user-submission-posts-plugin

Have already replied there, will repeat my reply here:

The plugin includes its own Challenge Question field, which can be enabled via the plugin settings. Adding a custom captcha is not yet supported, but is on the to-do list 🙂